Laminated ceramic electronic component

ABSTRACT

Provided is a laminated ceramic electronic component which has excellent mechanical characteristics, internal electrode corrosion resistance, high degree of freedom in ceramic material design, low cost, low defective rate, and various properties. The laminated ceramic electronic component includes: a laminate which has a plurality of laminated ceramic layers and Al/Si alloy-containing internal electrodes at a plurality of specific interface between ceramic layers; and an external electrode formed on the outer surface of the laminate, wherein the Al/Si ratio of the Al/Si alloy is 85/15 or more.

This is a continuation of application Serial Number PCT/JP2011/052528,filed Feb. 7, 2011, the contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a laminated ceramic electroniccomponent, such as that represented by a laminated ceramic capacitor,and more particularly relates to one including an internal electrodehaving an Al alloy as a component.

BACKGROUND ART

A laminated ceramic electronic component according to the presentinvention will be first described with reference to FIG. 1 using alaminated ceramic capacitor 1 as an example.

The laminated ceramic capacitor 1 includes a laminate 2 having aplurality of internal electrodes 4 and 5 formed along specificinterfaces between a plurality of laminated dielectric ceramic layers 3.

First and second external electrodes 6 and 7 are formed at differentlocations on the outer surface of the laminate 2. In the laminatedceramic capacitor 1 shown in FIG. 1, first and second externalelectrodes 6 and 7 are formed on opposite end surfaces of the laminate2. Internal electrodes 4 and 5 include a plurality of first internalelectrodes 4 electrically connected to the first external electrode 6and a plurality of second internal electrodes 5 electrically connectedto the second external electrode 7, and the first and second internalelectrodes 4 and 5 are arranged alternately with respect to thelaminating direction.

Various metal elements are conceivable for the internal electrode of thelaminated ceramic electronic component, but base metals are oftenconsidered for the purpose of cost reduction.

Since base metals are very easily oxidized when co-fired with a ceramic,it has been necessary to have a reducing atmosphere as the atmosphereduring firing and precisely control the temperature and oxygen partialpressure conditions. As a result, material design has been considerablylimited. In addition, there have been concerns about delaminationresulting from an uneven stress associated with co-firing, and so on.

In the case of using an internal electrode made of a base materialalone, there has been concern about the corrosion resistance of theinternal electrode if a ceramic laminate after being fired is exposed toa high-temperature and high-humidity environment.

Patent Document 1 discloses a laminated ceramic electronic componentusing a base metal alloy as an internal electrode material.Specifically, the base metal alloy is a Ni/Al alloy and a Ti/Al alloy.

Prior Art Patent Document

Patent Document 1: JP 6-84608 A

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

In the laminated ceramic electronic component in Patent Document 1, thefiring atmosphere is a nitrogen atmosphere, and therefore a re-oxidationtreatment of a ceramic material is required, so that the process iscomplicated.

Further, the laminated ceramic electronic component in Patent Document 1has the problem that a heavy stress is applied due to influences ofshrinkage behaviors during the reduction of the temperature in thefiring process, and thus delamination easily occurs.

Thus, an object of the present invention is to provide a laminatedceramic electronic component including an internal electrode made of abase metal alloy, wherein mechanical troubles such as delamination areinhibited, and firing can be performed even in air.

Means for Solving the Problem

The present invention is a laminated ceramic electronic componentincluding: a laminate which has a plurality of laminated ceramic layersand a plurality of internal electrodes formed at specific interfacesbetween ceramic layers and having an Al/Si alloy as a component; and anexternal electrode formed on the outer surface of the laminate, whereinthe Al/Si ratio of the Al/Si alloy is 85/15 or more.

Advantages of the Invention

According to the present invention, a laminated ceramic electroniccomponent can be obtained in which occurrence of delamination isinhibited because stresses applied to ceramic layers from internalelectrodes are low. In addition, a fixed amount of Si is contained in Alof the internal electrode to improve the corrosion resistance of theinternal electrode, so that a laminated ceramic electronic componenthaving high reliability even in a high-humidity environment can beobtained.

In addition, the laminated ceramic electronic component of the presentinvention is capable of being fired in air although the internalelectrode is made of a base metal, and therefore the degree of freedomin ceramic material design is improved. Accordingly, a laminated ceramicelectronic component having various properties can be obtained.

BRIEF EXPLANATION OF DRAWING

FIG. 1 is a view showing a laminated ceramic capacitor that is anexample of a laminated ceramic electronic component of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

A laminated ceramic electronic component of the present invention hasinternal electrodes having an Al/Si alloy as a main component. If theAl/Si ratio is 85/15 or more, the stress concentration between ceramiclayers and internal electrodes is relieved, so that a delaminationdefect is effectively suppressed.

If the laminated ceramic electronic component of the present inventionhas an oxygen partial pressure of 1×10⁻⁴ MPa or more (including thepressure of the air), the surface part of the internal electrode, i.e. asite contacting the ceramic layer, may be constituted by a layer havingAl₂O₃ as a main component. This results principally from oxidation ofthe surface of the Al internal electrode. This Al₂O₃ layer preventselectrode breakage of the Al internal electrode, and keeps theconductivity of the Al internal electrode satisfactory. This Al₂O₃ layeralso has an effect of smoothing the Al internal electrode layer. Forexhibiting these effects, the thickness of Al₂O₃ layer is preferably0.25% or more of the thickness of the internal electrode.

If the thickness of the Al₂O₃ layer is more than 10% of the thickness ofthe internal electrode, Al₂O₃ constitutes 20% of the total thickness ofthe internal electrode layer, and the improvement of the conductivity iscompromised. Accordingly, the thickness of Al₂O₃ layer is preferably 10%or less of the thickness of the internal electrode.

A method for producing the laminated ceramic electronic component of thepresent invention will now be described using a laminated ceramiccapacitor as an example.

First, a ceramic raw material is prepared. The ceramic raw material ismixed with an organic binder component and, as required, a solvent, andthereby formed into a ceramic slurry. By sheet-molding the ceramicslurry, a ceramic green sheet is obtained.

Next, an internal electrode having an Al/Si alloy as a main component isformed on the ceramic green sheet. For achieving this, there are severalmethods, among which the method of screen-printing in a desired patterna conductive paste containing an Al/Si alloy powder and an organicvehicle is convenient. In addition, there are the method of transferringa metal foil and the method of forming an Al/Si film while carrying outmasking by a vacuum thin film formation method.

In this way, ceramic green sheets and internal electrode layers arestacked in multiple layers, and brought into close contact with oneanother under pressure to thereby form a raw laminate before firing.

The raw laminate is fired in a kiln under a predetermined atmosphere andtemperature. For example, if the oxygen partial pressure during firingis 1×10⁻⁴ MPa or more and the firing temperature is 600° C. or more,oxidation of the surface of the internal electrode may proceed to forman Al₂O₃ layer having a moderate thickness. If the firing temperature is1,000° C. or less, electrode breakage of the internal electrode iseasily effectively prevented. Concerning the oxygen partial pressure,atmospheric pressure is most preferable when considering convenience ofthe process.

If the temperature increasing rate from room temperature to the maximumfiring temperature in the firing process is 100° C./minute or more, anAl₂O₃ layer is easily formed on the surface of the internal electrodemore reliably even though various changes, such as a change in ceramicmaterial composition, occur.

It is to be noted that Al has a melting point of about 660° C., but itcan be co-fired with a ceramic even at a temperature of 660° C. or moreaccording to the production method of the present invention. This isascribable to the Al₂O₃ layer formed on the surface part of the Alinternal electrode. Thus, a high degree of freedom is also provided forthe material composition design of the ceramic used, and a variety ofapplications can be covered.

It is to be noted that the ceramic composition in the laminated ceramicelectronic component of the present invention is not particularlylimited. A variety of materials can be applied within the bounds of notimpairing the object of the present invention, such as bariumtitanate-based materials (including those substituted with Ca, Sr, Zrand the like), lead titanate-based or lead zirconate titanate-basedmaterials, alumina-based glass ceramics, ferrites and transition elementoxide-based semiconductor ceramics.

The laminated ceramic electronic component of the present invention isapplicable not only to a laminated ceramic capacitor, but also to avariety of electronic components such as a laminated piezoelectricelement, a laminated thermistor element, a laminated chip coil, and aceramic multi-layered substrate.

EXAMPLE

In this Example, the Al/Si ratio in the internal electrode was changed,and effects thereof on delamination were examined. Three ceramicmaterials having different compositions were prepared.

First, powders of BaTiO₃, Bi₂O₃ and CuO were prepared as a first ceramicmaterial. These powders were mixed so as to satisfy the compositionratio described in “Material 1” in Table 1 to obtain a first ceramic rawmaterial.

Similarly, powders of Mn₃O₄, NiO, Fe₂O₃ and TiO₂ were prepared as asecond ceramic material. These powders were mixed so as to satisfy thecomposition ratio described in “Material 2” in Table 1 to obtain thesecond ceramic raw material.

Similarly, powders of BaTiO3, Bi₂O₃ and B₂O₃ were prepared as a thirdceramic material. These powders were mixed so as to satisfy thecomposition ratio described in “Material 3” in Table 1 to obtain a thirdceramic raw material.

An ethanol-based organic solvent and a polyvinyl butyral-based binderwere added to each of these ceramic raw materials, and the resultingmixture was mixed in a wet process by a ball mill to obtain a ceramicslurry. The ceramic slurry was sheet-molded to obtain a ceramic greensheet.

A series of Al/Si alloy powders with the Al/Si ratio within a range of99.9/0.1 to 83/17 as described in Table 1 was prepared. With the alloypowder were mixed an acetate-based organic solvent and a cellulose-basedbinder to obtain an Al/Si paste.

Next, an Al/Si paste with the Al/Si ratio within a range of 99.9/0.1 to83/17 was coated on each of the three ceramic green sheets by screenprinting to form an Al/Si paste layer. Ceramic green sheets coated withthe Al/Si paste were laminated so as to be arranged alternately in termsof the side to which the Al/Si paste layer extended, and brought intoclose contact with one another under pressure to obtain a raw laminate.

The raw laminate was heated in the air at 270° C. to remove the binder.Thereafter, the temperature was elevated at a temperature increasingrate of 100° C./minute, and the laminate was fired in air at the firingtemperature shown in Table 2. An Ag paste containing aBaO—SiO₂—BaO-based glass frit was coated on both end surfaces of theobtained laminate, and baked in the air at 600° C. to form externalelectrodes connected to the internal electrodes.

A laminated ceramic electronic component thus obtained had a length of2.0 mm, a width of 1.0 mm, a thickness of 1.0 mm, a thickness perceramic layer of 15 μm, a thickness per internal electrode layer of 5μm, and 30 effective layers contributing to an electrostatic capacity.The area of a portion confronted by the internal electrode per layer was1.7×10⁻⁶ m².

For each obtained sample, the electrostatic capacity and the dielectricloss (tan δ) were measured to find that it was practical as a laminatedceramic electronic component and there was no problem in conductivity ofthe internal electrode. A thin Al₂O₃ oxide film was formed on thesurface of the internal electrode made of the Al/Si alloy, and thesmoothness and the continuity of the internal electrode weresatisfactory.

Next, for 30 of each sample obtained, the presence/absence ofdelamination was inspected by ultrasonic flaw detection. A sample forwhich any delamination could be observed at all was considered as adefective, and the number of such samples is shown in Table 1.

TABLE 1 Firing Al/Si temperature Number of Material Material composition(atom) [° C.] defectives 1 90BaTiO₃ + 7Bi₂O₃ + 99.9/0.1 800 0/30 3CuO(mol %) 99/1 800 0/30 98/2 800 0/30 95/5 800 0/30 92/8 800 0/30  90/10800 0/30  88/12 800 0/30  85/12 800 0/30  83/17 800 6/30 2 18Mn₃O₄ +33NiO + 99.9/0.1 900 0/30 2.5Fe₂O₃ + 8TiO₂ (mol %) 99/1 900 0/30 98/2900 0/30 95/5 900 0/30 92/8 900 0/30  90/10 900 0/30  88/12 900 0/30 85/15 900 0/30  83/17 900 5/30 3 50BaTiO₃ + 10B₂0₃ + 99.9/0.1 750 0/3040Bi₂O₃ (vol %) 99/1 750 0/30 98/2 750 0/30 95/5 750 0/30 92/8 750 0/30 90/10 750 0/30  88/12 750 0/30  85/15 750 0/30  83/17 750 7/30

From the results in Table 1, it can be seen that the number ofdelamination defectives was 0 in samples in which the Al/Si ratio in theinternal electrode satisfied 99.9/0.1 to 85/15 in the laminated ceramiccapacitors using the three ceramic materials described above. On theother hand, a delamination defect occurred for samples having an Al/Siratio of less than 85/15.

Industrial Applicability

A laminated ceramic electronic component of the present invention isapplicable for a laminated ceramic capacitor, a laminated piezoelectricelement, a laminated thermistor, a laminated chip coil, a ceramicmulti-layered substrate and the like.

The invention claimed is:
 1. A laminated ceramic electronic componentcomprising a laminate comprising a plurality of laminated ceramic layersand a plurality of Al/Si alloy-containing internal electrodes eachdisposed at a respective one of a plurality of specific interfacesbetween the plurality of ceramic layers, wherein the Al/Si atomic ratioin the Al/Si alloy is 85/15 or more.
 2. The laminated ceramic electroniccomponent according to claim 1, wherein at least one internal electrodehas a layer of Al₂O₃ on its surface.
 3. The laminated ceramic electroniccomponent according to claim 2, wherein the Al₂O₃ constitutes 0.25% to10% of the thickness of the internal electrode.
 4. The laminated ceramicelectronic component according to claim 3, wherein the ceramic comprisesa titanate, zirconate, glass ceramic, ferrite or transition elementoxide ceramic.
 5. The laminated ceramic electronic component accordingto claim 4, further comprising at least one external electrode on anouter surface of the laminate.
 6. The laminated ceramic electroniccomponent according to claim 3, further comprising at least one externalelectrode on an outer surface of the laminate.
 7. The laminated ceramicelectronic component according to claim 2, further comprising at leastone external electrode on an outer surface of the laminate.
 8. Thelaminated ceramic electronic component according to claim 1, furthercomprising at least one external electrode on an outer surface of thelaminate.
 9. The laminated ceramic electronic component according toclaim 1, wherein the Al/Si atomic ratio in the Al/Si alloy is 88/12 to99.9/0.1.
 10. The laminated ceramic electronic component according toclaim 9, wherein at least one internal electrode has a layer of Al₂O₃ onits surface.
 11. The laminated ceramic electronic component according toclaim 10, wherein the Al₂O₃ constitutes 0.25% to 10% of the thickness ofthe internal electrode.
 12. The laminated ceramic electronic componentaccording to claim 1, wherein the ceramic layer comprises a bariumtitanate-based perovskite compound, and the laminated ceramic electroniccomponent is a laminated ceramic capacitor.
 13. The laminated ceramicelectronic component according to claim 12, further comprising at leastone external electrode on an outer surface of the laminate.
 14. Thelaminated ceramic electronic component according to claim 13, wherein atleast one internal electrode has a layer of Al₂O₃ on its surface. 15.The laminated ceramic electronic component according to claim 14,wherein the Al₂O₃ constitutes 0.25% to 10% of the thickness of theinternal electrode.
 16. The laminated ceramic electronic componentaccording to claim 1, wherein the ceramic layer comprises a Mn—Ni—Fe—Tioxide-based compound, and the laminated ceramic electronic component isa laminated chip coil.
 17. The laminated ceramic electronic componentaccording to claim 16, further comprising at least one externalelectrode on an outer surface of the laminate.
 18. The laminated ceramicelectronic component according to claim 17, wherein at least oneinternal electrode has a layer of Al₂O₃ on its surface.
 19. Thelaminated ceramic electronic component according to claim 18, whereinthe Al₂O₃ constitutes 0.25% to 10% of the thickness of the internalelectrode.
 20. The laminated ceramic electronic component according toclaim 11, wherein each of the plurality of Al/Si alloy-containinginternal electrodes contact both of adjacent ceramic layers forming thespecific interfaces.